Pilot-operated steam traps

ABSTRACT

A pilot-operated steam trap is provided with a series of bimetallic elements which operate sequentially to control the opening and closing of the pilot valve of a pilot-operated steam trap. Each separate series of the bimetallic elements have their outer edges on separate shoulders within the valve member and have central openings through which the stem of the pilot valve passes. Separate shoulders are provided on the stem of the pilot valve, each adapted to be engaged by one of the series of bimetallic elements to prevent transmission of the force of one bimetallic element to the next adjacent bimetallic element.

United States Patent [191 Wichtel PILOT-OPERATED STEAM TRAPS [75]Inventor: Alejandro Wichtel, Wyncote, Pa. [73] Assignee: YarwayCorporation, Blue Bell, Pa.

[22] Filed: Apr. 27, 1973 [21] Appl. No.: 355,274

Related us; Application Data [63] Continuation of Ser. No. 200,810, Nov.22, 1971,

[451 Feb. 5, 1974 3/1965 Pape et al. 236/59 2/1965 Domm et al. 236/59[57] ABSTRACT A pilot-operated steam trap is provided with a series ofbimetallic elements which operate sequentially to control the openingand closing of the pilot valve of a pilot-operated steam trap. Eachseparate series of the bimetallic elements have their outer edges onseparate shoulders within the valve member and have central openingsthrough which the stem of the pilot valve passes. Separate shoulders areprovided on the stem of the pilot valve, each adapted to be engaged byone of the series of bimetallic elements to prevent transmission of theforce of one bimetallic element to the next adjacent bimetallic element.

6 Claims, 4 Drawing Figures PILOT-OPERATED STEAM TRAPS This is acontinuation of application Ser. No. 200,810, filed Nov. 22, 1971, nowabandoned.

The present invention relates to new and useful improvements inpilot-operated steam traps and more particularly to improvements in themeans for actuating and controlling the pilot valves of such steamtraps.

In application Ser. No. 136,493, filed Apr. 23, 1971, now abandoned, byWarren H. Brand and John Scott, Jr., and assigned to the assignee of thepresent application, there is disclosed a pilot-operated steam trap inwhich the pilot valve is controlled by a temperature responsive bellows.The arrangement of bimetallic elements of the present invention providesa different control of the pilot valve over the normal condensate loadrange from the structure of the above application. Bimetallic elementshave previously been used to control operation of a steam trap. Anexample of this is the Domm et al US. Pat. No. 3,169,704. In Domm,however, the elements must be in opposed pairs and work against oneanother. Also, in the construction of the Domm patent the force tocontrol the valve is transmitted from one set of bimetallic elements tothe next set thereby unnecessarily stressing each bimetallic element.

With the foregoing in mind, a primary object of the 'present inventionis to provide a novel pilot-operated Another object of the presentinvention is to provide a novel pilot-operated steam trap having theability to handle heavy condensate loads but which will also providegood control with light condensate loads.

A further object of the present invention is to provide novel controlmeans for a pilot-operated steam trap which will closely follow thesaturation curve of the fluid in the trap.

When the condensate load on a conventional steam trap is low, up toapproximately 10 percent of rated capacity, the steam trap is normallynot in good control. It is an object of this invention to provide animproved steam trap which will properly control the flow of condensateWithin this normally uncontrollable low range of operation.

A still further object of the present invention is to tional view of thepilot valve with the pilot in a partially open position;

FIG. 3 is an exploded perspective view showing the assembly of thebimetallic elements for controlling the pilot valve of the steam trap;and

FIG. 4 is a chart illustrating how the pilot operation closely followsthe steam saturation curve.

Referring more specifically tothe drawings, there is illustrated in FIG.1 a steam trap made in accordance with the present invention. The steamtrap 10 includes a trap body 11 having an inlet 12 adapted to beconnected to a suitable steam line from which condensate is to bedrained and an outlet 13 connected to a suitable condensate line. Acontrol chamber 14 is probonnet 15 mounted on the valve body 11.

1 valve assembly 16 is adapted to seat on a main valve provide a steamtrap which will provide modulation of control over the normal condensateload and when the condensate load gets above normal will rapidlydischarge the excess condensate.

An additional object of the present invention is to provide novelcontrol means for the pilot valve of a pilot-operated steam trap whichwill control movement of the pilot valve in such a manner to preventwire drawing of the pilot valve and valve seat.

Still a further object of the present invention is to provide a novelpilot-operated steam trap which is easy to assemble and in which thecontrol means for the pilot can be easily inserted or replaced and theposition of the pilot valve can be easily adjusted.

A further object of the present invention is to provide a novelpilot-operated steam trap which may be manufactured and assembled easilyand economically and which is entirely efficient and effective inoperation.

These and other objects of the present invention and the variousfeatures and details thereof are hereinafter seat 17 surrounding anupturned portion 13a of the outlet 13 to control flow of fluid throughthe trap. In the illustrated embodiment of the present invention themain valve assembly 16 is in the form of a hollow piston havingcircumferentially-extending axially-spaced upper and lower ribs 18 and19 which closely fit within the inner cylindrical surface 20 of thebonnet 15. A surface 21 is provided at the lower end of the main valveassembly to engage the main valve seat 17. It should be understood thatthe surface 21 and seat 17 may be of any desired configuration tocontrol flow of fluid through the steam trap. The main valve assembly 16is adapted to slide longitudinally within. the bonnet 15 to permitopening and closing of the steam trap.

. According to the present invention, a pilot valve 22 carried by avalve stem 23 is provided extending through a central opening 24 in thebottom of the main valve assembly 16. The pilot valve 22 is adapted toengage against a pilot valve seat 25 in the opening 24 to control flowof fluid from the control chamber 14 to the steam trap outlet 13.

In the illustrated embodiment of this invention, the main valve assembly16 is displaced axially in response to the application of pressureforces on opposite ends of the main valve assembly. To properly controldisplacement of the main valve assembly, a first control flow passage offixed resistance to flow is provided by I the clearance between theouter periphery of the main valve assembly and the inner surface 20 ofthe bonnet 15. This first control flow passage permits fluidcommunication between the inletl2 and the upper portion of the controlchamber 14. A second control flow passage from the control chamber 14 tothe outlet 13 is provided through the central opening 24 in the mainvalve assembly. This second control flow passage provides a variableresistance to flow depending upon the position of the pilot valve 22relative to the pilot valve seat 25. The fixed resistance to flow of thefirst control flow passage must necessarily be equal to or greater thanthe resistance to flow through the second control flow passage when thepilot valve is in its fully open position but substantially less thanthe resistance to flow through the second flow control passage when thepilot valve is less than fully open to permit operation of the mainvalve assembly as more fully set forth hereinafter.

When the pilot valve 22 is closed, the fluid pressure within the controlchamber 14 will be substantially equal to the fluid pressure at theinlet 12 and the main valve assembly will remain in its closed position.Opening the pilot valve will vent fluid from the control chamber 14 tothe outlet 13. Fluid will continue to flow through the first controlflow passage into the control chamber and then through the secondcontrol flow passage (the opening 24) to the outlet. Continued openingof the pilot valve increases the size of the second control flow passagecausing further decrease of pressure within the control chamber. After apredetermined pressure drop which will occur when the resistance to flowof the second control flow passage is substantially equal to theresistance to flow of the first control flow passage, the main valveassembly will be caused to move to its open position permitting flow of.fluid directly from the inlet to the outlet across the valve seat 17.Similarly, upon closing the pilot valve 22, resistance to flow throughthe opening 24 or second control flow passage increases therebydecreasing flow through the opening 24 and permitting pressure in thecontrol chamber to increase. At a predetermined pressure within thecontrol chamber the main valve assembly will move to the closed positionstopping flow across the valve seat 17.

It is extremely desirable that the pilot valve and pilot valve seat beof such a size that they will accommodate approximately to 25 percent ofthe total capacity of the flow of the steam trap. This permits flow ofcondensate through the pilot valve in the low range of capacity of thesteam trap. Thus, there can be good modulation and control of flow ofcondensate through the steam trap at the normally unstable low range ofcapacity of the trap. When the requirement for flow of the condensate isgreater than the limited capacity of the pilot valve, the pilot valvewill be in its fully open position and the main valve assembly willopen, thus permitting this greater quantity of condensate to flowdirectly from the inlet to the outlet across the main valve seat 17.This construction is particularly advantageous for use in situationswhere there is a greatly varying condensate load required to be handledby the steam trap.

In accordance with the present invention the position of the pilot valve22 relative to the pilot valve seat 25 is controlled in accordance withthe temperature of the fluid within the control chamber 14. When steamis present in the control chamber 14, the pilot valve will closepreventing flow of fluid through the trap. As the temperature in thecontrol chamber 14 drops and condensate is present at the steam trap,the pilot valve will open permitting this condensate to be dischargedthrough the trap. Accordingly, a thermal responsive control means isprovided to control the position of the pilot valve.

In the present invention, the thermal responsive control means forcontrolling the position of the pilot valve comprises a series ofbimetallic elements in engagement with inner shoulders on the main valveassembly 16 and interconnected independently to the pilot valve stem 23.As illustrated in FIGS. 1, 2 and 3 of the drawings, three separatevertically spaced bimetallic elements are provided designated from theupper to the lower as 26, 27 and 28. The upper, intermediate and lowerbimetallic elements 26, 27, 28 are loosely engaged on upwardly facingshoulders 29, 30 and 31, respectively, provided on the inner surface ofthe main valve assembly 16. Each of the three bimetallic elements 26, 27and 28 are normally in the substantially flat condition as shown in FIG.1 at usual room temperatures. These bimetallic elements will deflectupwardly at varying rates as more fully described hereinafter upon anincrease in temperature within the control chamber 14. The bimetallicelements 26, 27 and 28 are of different size, shape and thickness sothat the magnitude or rate of deflection and force exerted upondeflection of the upper bimetallic element 26 in response to a change intemperature is different than that of the intermediate bimetallicelement for a corresponding change in temperature. Similarly, themagnitude or rate of deflection and force exerted upon deflection of theintermediate bimetallic element for this same change in temperature isdifferent from that of the lower bimetallic element 28 for thiscorresponding change in temperature.

In order to permit control of the position of the pilot valve 22 withrespect to the pilot valve seat 25 by the bimetallic elements 26, 27 and28, an adjustable stop such as the nut 32 is secured onto the upper endof the pilot valve stem 23. This adjustable stop is adapted to have itslower surface engaged by the upper bimetallic element 26 and is soadjusted that when the upper bimetallic element 26 is in its flat orundeflected condition as it would exist at a low temperature, the pilotvalve 22 is fully open. A stepped sleeve 33 is loosely received aboutthe pilot valve stem 23. The stepped sleeve 33 passes through centralopenings in the upper and intermediate bimetallic elements 26 and 27 andhas an intermediate downwardly facing shoulder 34 thereon adapted toengage against the upper surface of the intermediate bimetallic element27. The lower surface 35 of the stepped sleeve 33 is adapted to engageagainst the upper surface of the lower bimetallic element 28.

During operation of the steam trap of the present invention, when steamor very hot liquid is present in the control chamber, the bimetallicelements are deflected upwardly and the pilot valve is held closed bythe force applied to the valve stem by the bimetallic elements. When thetemperature in the control chamber is relatively low as it would be whencondensate is flowing through the steam trap, the bimetallic elementsare in their substantially flat or undeflected condition and the pilotvalve is fully open. Assuming that condensate is flowing through thesteam trap and the pilot valve is fully open the steam trap operates inthe following manner. As the temperature within the control chamberincreases, each of the bimetallic elements deflect upwardly at thepreviously-described varying rates. The upper bimetallic element 26 willinitially engage the lower surface of the adjustable stop 32 and forcethe valve stem upwardly moving the pilot valve toward its closedposition. Depending upon the pressure within the system to which thesteam trap is connected, the upper bimetallic element will'move thepilot valve to its fully closed position at a low system pressure or topartially closed position to the point where the force exerted bydeflection of the upper bimetallic element is no longer capable ofovercoming the pressure in the system forcing the pilot valve open. Uponcontinued increase in temperature, the intermediate bimetallic elementwill engage against the shoulder 34 of the sleeve 33 and force thesleeve 33 upwardly against the adjustable stop 32 and add additionalforce on the pilot valve to hold the pilot valve closed or to urge thepilot valve toward the closed position, again depending on the pressurewithin the system. Upon a further increase in temperature the lowerbimetallic element 28 will engage against the lower surface 35 of thestepped sleeve 33 thereby exerting further force to close and maintainthe pilot valve closed. Thus, when steam or very hot liquid is presentin the control chamber, all three of the bimetallic elements areexerting force through the valve stem to maintain the pilot valveclosed.

Similarly, after the pilot valve is fully closed and condensate iscollected at the trap, as the temperature in the control chamber isdecreased the three bimetallic elements 26, 27 and 28 will'operate inreverse of the I above-described method to permit movement of the pilotvalve toward the fully open position. All of the bimetallic elementswill move from their fully deflected position toward the substantiallyflat position at the previously-described varying rates. As thetemperature decreases, the lower bimetallic element will becomedisengaged from the lower surface 35 of the sleeve 33 before theintermediate bimetallic element becomes disengaged from the shoulder 34of the sleeve 33. Similarly, the intermediate bimetallic element becomedisengaged from the shoulder 34 of the sleeve 33 before the upperbimetallic element reaches its substantially flat position. Thus, as thetemperature in the control chamber decreases, the force applied by thebimetallic elements to hold the pilot valve in any fixed positiondecreases. The pilot valve will open when the force exerted on the pilotvalve by the pressure within the control chamber is sufficient toovercome the force exerted by the bimetallic elements on the stem of thepilot valve. When the pilot valve is closed, the effective forcedue topressure within the control chamber tending to move the pilot valvetoward its open position is equal to the pressure within the controlchamber times an area equal to the area of the opening 24. This forceincreases slightly after the pilot valve is partially opened because ofthe configuration of the pilot valve and the restricted area immediatelydownstream of the valve seat 25. This effectively provides a slightlylarger area than the area of the opening 24 on which the pressure withinthe chamber operates, thereby moving the pilot valve rapidly away fromthe valve seat 25 and preventing wire drawing of the valve and valveseat. Upon continued decrease in temperature within the control chamber,the force exerted on the pilot valve by the bimetallic elements on thepilot valve decreases thereby permitting further opening of the pilotvalve toward its fully open position.

This above-described arrangement of bimetallic elements for controllingmovement of the pilot valve is particularly desirable in that because ofthe different rates of deflection and the different combinations oftemperatures and pressures at which the bimetallic elements disengagefrom the valve stem, movement of the line in FIG. 4 is a representationof the steam saturation curve while the dotted line which closelyfollows along the steam saturation curve from 0 to a to b to crepresents force exerted on the pilot valve by the bimetallic elements.From 0 to a, the force on the pilot valve is due to the bimetallicelement 26. From a to b, the force exerted on the pilot valve is by theupper and intermediate bimetallic elements while from b to c the forceexerted on the pilot valve is produced by all three bimetallic elements.Thus, the pilot valve is extremely responsive to the temperature withinthe control chamber and its movement at any position lags only a veryshort distance behind the saturation temperature of fluid within thecontrol chamber.

While a particular embodiment of the present inventionhas beenillustrated. and described herein, it is apparent that various changesand modifications may be made to the described structure. For example,two or four or more bimetallic elements may be utilized, though thethree described elements provide a most satisfactory operation of thepilot valve. Also, other thermostatic elements or groups of elements maybe substituted for the individual bimetallic elements.

From the foregoing, it can be seen that the present invention provides anovel pilot-operated steam trap of a relatively simple constructionwhich closely controls low rates of condensate flow yet permits a highrate of condensate flow when necessary.

I claim:

1. A pilot operated steam trap having a body with an inlet and anoutlet, means providing a control chamber within said body intermediatethe inlet and the outlet, a main valve seat between the inlet andoutlet, a generally cylindrical main valve member carried within thecontrol chamber for axial movement toward and away from said main valveseat, said main valve member having a valve portion on one end surfacethereof to engage said valve seat and having means defining a recessextending into said main valve member from the other end surfacethereof, a first flow control passage of substantially fixed restrictionto flow providing fluid communication between the inlet and the controlchamber, a second flow control passage through said one end surfaceofsaid main valve member providing fluid communication betweenthecontrolchamber and the outlet,'a pilot valve controlling said secondflow control passage mounted for movement between closed and openpositions, said pilot valve in the fully open position providing saidsecond flow control passage with less restriction to flow than saidfirst flow control passage, a plurality of independent spaced aparttemperature responsive elements in said control chamber supported by andmovable with said main valve member, means defining a plurality ofstepped shoulders corresponding in number to said plurality oftemperature responsive elements on said main valve member within saidrecess, each of said temperature responsive ele ments having outer edgeportions loosely engaged on a corresponding shoulder in said main valvemember recess, a stem interconnected with said pilot valve andprojecting upwardly centrally of said main valve member recess, saidelements each having a central opening therein surrounding said pilotvalve stem, means defining a plurality of shoulders corresponding innumber to said plurality of temperature responsive elements about saidpilot valve stem with each of said shoulders facing in a directionopposite the shoulders of said main valve member recess, saidtemperature responsive elements each having an inner edge surfacesurrounding its central opening adapted to engage the correspondingshoulder of said stem between said open and closed positions, each ofsaid plurality-of temperature responsive elements adapted to aid incontrol of movement of said pilot valve, one of said temperatureresponsive elements adapted to aid in control of movement of said pilotvalve from its fully open position to its fully closed position, and atleast one other said'temperature responsive elements adapted to aid incontrol of movement of said pilot valve from a partially open positionto its fully closed position.

2. Apparatus in accordance with claim 1 in which said temperatureresponsive elements are bimetallic plates. 7

3. Apparatus in accordance with claim 2 in which an adjustable stopmember is provided on said pilot valve stem forming one of said pilotvalve stem shoulders and defining the positions of the remaining of saidplurality of pilot valve stem shoulders, and one of said bimetallicplates is in engagement with its corresponding shoulder of said pilotvalve stem when steam is present in said 8 control chamber to urge saidpilot valve toward said closed position when steam is present in saidcontrol chamber.

4. Apparatus in accordance with claim 3 in which another of saidbimetallic plates is forceably interconnected with its correspondingpilot valve stem shoulder after a predetermined amount of deflection ofsaid one bimetallic plate.

5. Apparatus in accordance with claim 4 in which said bimetallic platesare-substantially flat at lower temperatures in the control chamber anddeflect from the flat condition in the same direction upon an increasein temperature in the control chamber.

6. Apparatus in accordance with claim 5 in which said one bimetallicplate has a greater rate of deflection and greater amount of deflectionthan said other bimetallic plate for the same change in temperature insaid control chamber.

1. A pilot operated steam trap having a body with an inlet and anoutlet, means providing a control chamber within said body intermediatethe inlet and the outlet, a main valve seat between the inlet andoutlet, a generally cylindrical main valve member carried within thecontrol chamber for axial movement toward and away from said main valveseat, said main valve member having a valve portion on one end surfacethereof to engage said valve seat and having means defining a recessextending into said main valve member from the other end surfacethereof, a first flow control passage of substantially fixed restrictionto flow providing fluid communication between the inlet and the controlchamber, a second flow control passage through said one end surface ofsaid main valve member providing fluid communication between the controlchamber and the outlet, a pilot valve controlling said second flowcontrol passage mounted for movement between closed and open positions,said pilot valve in the fully open position providing said second flowcontrol passage with less restriction to flow than said first flowcontrol passage, a plurality of independent spaced apart temperatureresponsive elements in said control chamber supported by and movablewith said main valve member, means defining a plurality of steppedshoulders corresponding in number to said plurality of temperatureresponsive elements on said main valve member within said recess, eachof said temperature responsive elements having outer edge portionsloosely engaged on a corresponding shoulder in said main valve memberrecess, a stem interconnected with said pilot valve and projectingupwardly centrally of said main valve member recess, said elements eachhaving a central opening therein surrounding said pilot valve stem,means defining a plurality of shoulders corresponding in number to saidplurality of temperature responsive elements about said pilot valve stemwith each of said shoulders facing in a direction opposite the shouldersof said main valve member recess, said temperature responsive elementseach having an inner edge surface surrounding its central openingadapted to engage the corresponding shoulder of said stem between saidopen and closed positions, each of said plurality of temperatureresponsive elements adapted to aid in control of movement of said pilotvalve, one of said temperature responsive elements adapted to aid incontrol of movement of said pilot valve from its fully open position toits fully closed position, and at least one other said temperatureresponsive elements adapted to aid in control of movement of said pilotvalve from a partially open position to its fully closed position. 2.Apparatus in accordance with claim 1 in which said temperatureresponsive elements are bimetallic plates.
 3. Apparatus in accordancewith claim 2 in which an adjustable stop member is provided on saidpilot valve stem forming one of said pilot valve stem shoulders anddefining the positions of the remaining of said plurality of pilot valvestem shoulders, and one of said bimetallic plates is in engagement withits corresponding shoulder of said pilot valve stem when steam ispresent in said control chamber to urge said pilot valve toward saidclosed position when steam is present in said control chamber. 4.Apparatus in accordance with claim 3 in which another of said bimetallicplates is forceably interconnected with its corresponding pilot valvestem shoulder after a predetermined amount of deflection of said onebimetallic plate.
 5. Apparatus in accordance with claim 4 in which saidbimetallic plates are substantially flat at lower temperatures in thecontrol chamber and deflect from the flat condition in the samedirection upon an increase in temperature in the control chamber. 6.ApparatUs in accordance with claim 5 in which said one bimetallic platehas a greater rate of deflection and greater amount of deflection thansaid other bimetallic plate for the same change in temperature in saidcontrol chamber.